Gallium nitride thin film crystal draws attention as excellent blue light-emitting devices, has been used as a material for light-emitting diodes and expected as a blue-violet semiconductor laser device for an optical pickup.
According to Japanese Patent Publication Nos. 2004-182551A and 2005-12171A, when an underlying film of a single crystal is formed on a substrate by flux method, the underlying film is divided to island shaped films and films of gallium nitride single crystal is then formed on the island-shaped underlying films.